Binders or binder systems for foundry cores and molds are well known. In the foundry art, cores or molds for making metal castings are normally prepared from a mixture of an aggregate material, such as sand, and a binding amount of a binder or binder system. Typically, after the aggregate material and binder have been mixed, the resulting mixture is rammed, blown or otherwise formed to the desired shape or pattern, and then cured with the use of catalysts and/or heat to a solid, cured state.
Resin binders used in the production of foundry molds and cores are often cured at high temperatures to achieve the fast-curing cycles required in foundries. However, in recent years, resin binders have been developed which cure at low temperatures, to avoid the need for high-temperature curing operations which have higher energy requirements and which often result in the production of undesirable fumes.
One group of processes which do not require heating in order to achieve curing of the resin binder are referred to as "cold-box" processes. In such processes, the binder components are coated on the aggregate material, such as sand, and the material is blown into a box of the desired shape. Curing of the binder is carried out by passing a gaseous catalyst or hardener at ambient temperatures through the molded resin-coated material
One such "cold-box" process employs an aqueous alkaline solution of a phenolic resole resin as the binder. This binder is cured by passing the volatile ester through the molded resin-coated material. The process is described in detail in U.S. Pat. No. 4,468,359 (Re. 32,720) which is incorporated herein by reference in its entirety.
The ester cured process is superior to some of the earlier processes from an environmental standpoint. However, the tensile strengths of the cores made by this process tend to be somewhat lower than those prepared by other "cold-box" processes. Previous workers have sought to improve the strength of the cores obtained using the ester cure process by adding modifiers to the resin. Such modifiers include: ketone alcohols and ether alcohols such as furfuryl alcohol and monoalkyl ethers of glycols or diglycols, U.S. Pat. No. 4,780,489.
We have now discovered that certain phenoxyethanols, not hitherto used with ester-cured phenolic binder systems, speed the rate of cure of such systems, giving molds and cores with higher tensile strength. This reduces breakage of the cores when they are removed from the core boxes and handled. Furthermore, they are useful at low levels minimizing organic emissions and volume of gas generated on pouring. This reduces gas related defects.